Imaging apparatuses that employ optical coherence tomography (hereinafter referred to as OCT) are being developed (see PTL 1) (hereinafter, an imaging apparatus that employs OCT is referred to as an OCT apparatus). An OCT apparatus illuminates an object with light while changing the wavelength of the illumination light and makes reflection light beams returned from different depths of the object interfere with reference light to generate interference light. Then, frequency components of the temporal waveform representing the intensity of the interference light are analyzed to thereby obtain a tomographic image of the object. An OCT apparatus is used in fundus examinations, for example.
A large number of ocular diseases are difficult to completely cure. Therefore, it is important to find any lesion in the fundus earlier and to start a treatment that slows the spreading of the lesion over a wide area of the fundus earlier. Particularly, if the lesion reaches the macula, vision is seriously impaired. Therefore, it is desirable to find any lesion even if the lesion is located sufficiently away from the macula. To meet such a desire, an OCT apparatus used in fundus examinations is expected to have a wider angle of view.
PTL 1 discloses a technique for creating a tomographic image of a wide area by combining together a plurality of tomographic images in order to widen the area of the fundus which is observable on the tomographic image. PTL 1 also discloses an OCT apparatus that employs a swept light source (a swept-source OCT apparatus, hereinafter referred to as an SS-OCT apparatus). According to PTL 1, the swept light source is constituted by a fiber-ring resonator and a wavelength-selective filter, for example.